One method of wet spinning fibers is called air gap spinning (or alternately "dry-jet wet spinning"), and it is particularly useful for spinning aramid fibers from solutions of aramids. Such processes are well known in the art, see for instance U.S. Pat. Nos. 3,767,756 and 15 3,869,429, and B. Huang, et al., Zhongquo Fangzhi Daxue Xuebao, vol. 16, p. 23-30 (1990), all of which are hereby included by reference.
In air gap spinning, a solution of a polymer such as an aramid is forced through a spinneret. The face of the spinneret is in contact only with a gas, usually air. After travelling a short distance through the air, typically 0.1-10 cm., the solution (in the form of a fine "jet") enters a coagulant, which extracts the solvent from the polymer, resulting in the formation of a polymer fiber. Often this coagulant is water based, although anything that is miscible with the material that the polymer is dissolved in, and in which the polymer is insoluble and preferably does not swell appreciably, may be used. Importantly, in the gap between the spinneret face and the coagulant, the fiber solution, which is usually quite viscous and somewhat viscoelastic, is drawn, resulting in a smaller diameter jet of aramid solution entering the coagulant than was extruded from the spinneret holes.
The amount of drawing that can be done is limited, because above some maximum draw value fiber physical properties such as tensile strength, start to decrease. In the invention described herein, use of a drag reducer in the coagulant bath allows higher draw ratios to be achieved in the spinning process without deleterious effects on fiber physical properties.
U.S. Pat. No. 4,529,763 discloses that coagulant baths may contain relatively high amounts, preferably 30% or more, polyalkylene oxides, and no mention is made of using very high molecular weight polyalkylene oxides.
Japanese Patent 76-118323 describes a spinning process in which the coagulating bath is a pure polyalkylene glycol, preferably polyethylene glycol.